A wide range of phytopathogenic fungi exist causing various plant diseases, which can lead to devastating economic, environmental, and social impacts on a global scale. One such fungus is Pyrrhoderma noxium, causing brown root rot disease in over 200 plant species of a variety of life forms mostly in the tropical and subtropical regions of the globe. The aim of this study was to discover the antagonistic abilities of two Trichoderma strains (#5001 and #5029) found to be closely related to Trichoderma reesei against P. noxium. The mycoparasitic mechanism of these Trichoderma strains against P. noxium involved coiling around the hyphae of the pathogen and producing appressorium like structures. Furthermore, a gene expression study identified an induced expression of the biological control activity associated genes in Trichoderma strains during the interaction with the pathogen. In addition, volatile and diffusible antifungal compounds produced by the Trichoderma strains were also effective in inhibiting the growth of the pathogen. The ability to produce Indole-3-acetic acid (IAA), siderophores and the volatile compounds related to plant growth promotion were also identified as added benefits to the performance of these Trichoderma strains as biological control agents. Overall, these results show promise for the possibility of using the Trichoderma strains as potential biological control agents to protect P. noxium infected trees as well as preventing new infections.

Brown root-rot disease is caused by phytopathogenic white-rot basidiomycete fungus, Pyyrhoderma noxium. Currently, it is causing significant issues for the Brisbane hinterland in Queensland, Australia and killing many tree species throughout the greater Metropolitan area, including park and street trees located in Shorncliffe, Taringa, New Farm, Eagle Farm, West End, Hamilton, Indooroopilly, Brisbane River, and the City Centre. Brisbane trees being attacked are figs, poinciana, jacarandas, Chinese elms, Moreton Bay eucalypts, kauris, and hoop pines and these include both public and privately owned trees. A joint study between the University of the Sunshine Coast (UniSC) and the Brisbane City Council (BCC) aimed to assess the efficacy of different biological control agents to control infections in the region. In a substudy presented here, termite gut-associated actinomycetes were evaluated to determine their antifungal abilities against the pathogen.